Regal Entertainment, the country's largest circuit, also hasn't struck a new deal with Disney -- which hasn't revisited terms since it acquired Pixar and Marvel, home of Iron Man 3. The threequel, returning with Robert Downey Jr. in the title role, is set to open May 3.

AMC is the country's second-largest theater circuit.

Insiders say they expect all sides to come to an agreement in the next few days. The talks are taking place in Las Vegas, where exhibitors and studios are gathered together this week for CinemaCon, the annual convention of theater owners.

"This will get worked out. And while advance tickets sales are great, everyone is going to find this movie," said one insider. "This is not a boycott."